Successful Laboratory Rearing –A tool for conservation of Indian , gigas Gobinda Ch. Biswal, Siddhartha Pati and Bisnu P. Dash

3rd International workshop on the science & conservation of Horseshoe crabs

Gobinda Chandra Biswal Head, Department of Zoology, S. College, Amarda Road And Department of Biosciences and Biotechnology Fakir Mohan University Balasore, Odisha, India Introduction

 The horseshoe crabs are benthic and descended from mud dwelling primitive called trilobite which lived in the Precambrian seas, nearly 600 million years ago (Price, 1971).  In India, the horseshoe crabs regularly migrate towards the shore for the purpose of breeding (Mikkelsen, 1988; Kelsey and Hassall, 1989; Chatterji, 1994).  In the world, the horseshoe crabs are now represented by four existing species (Sekiguchi and Nakamura 1979).  The Indian horseshoe crab i.e. T.gigas & C. rotundicauda are found in east coast of India extending from West Bengal up to Andhra Pradesh. But T. gigas are abundantly available in north- east coast of Odisha extending from Subarnarekha estuary up to Kansha estuary.  But at present it is a major concern that the population of all the species is in a declining trend. But the reasons for the population depletion for all species and the degree of their exploitation are mainly manmade.  There is need to study breeding biology of these Indian horseshoe crabs available in Odisha as they are in a different geographical area. Worldwide distribution Objectives

Hatching and captive rearing of Indian horseshoe crab Tachypleus gigas under laboratory condition. To gain Knowledge about the breeding biology of these valuable animals. To save the endangered populations of this species from extinction by sea releasing Materials and Methods

• Selection of nesting ground • Identification of nests • Collection and separation of viable • Incubation of eggs • Hatching of larvae • Rearing of larvae Amplexed horseshoe crab Identification of nest by reprints Collection of Separation of eggs from eggs nest Incubation of collected eggs in laboratory condition

Damaged eggs Molting of embryo

Exuvia

Hatching of trilobite larvae

Larva to be hatched

Newly hatched

Peri -viteline membrane

First molting – second instar larvae

Second instar larva

Exuvium of first molting FEEDING MOVEMENT OF LARVAE Second molting –third instar larvae

Prosoma

Opisthosoma

Telson

Exuvium of second molting RESULTS AND DISCUSSION

Eggs collected from MAHISALI ESTUARY HATCHING AT 26 c TEMP. AND 25 PPT SALINITY AND TIME TAKEN 35-42 DAYS

NEST DIAMETER DEPTH OF NO. OF EGGS NO. OF NO OF FIRST % OF FIRST NO OF % OF NO OF THIRD % OF THIRD OF NEST(CM) THE DEFECTIVE INSTAR INSTAR SECOND SECOND INSTART INSTAR NEST(CM) EGGS LARVAE LARVAE INSTAR INSTAR LARVAE LARVAE LARVAE LARVAE

A 18 9 85 5 77 96% 76 98% 74 97%

B 19 9 102 7 92 97% 90 98% 87 96% C 22 10 128 8 116 97% 115 99% 112 97%

SUCCESS RATE OF REARING

1 0.99 0.98 0.97

0.96 SUCCESS SUCCESS RATE 0.95 0.94 % OF EGGS COLLECTED % OF FIRST INSTAR % OF SECOND INSTAR % OF THIRD INSTAR

DIFFERENT STAGES RESULTS AND DISCUSSION

 The fertilized eggs were hatched as per the natural reported time period of 42 days of incubation and with a hatching rate of 98.0%. Trilobites have molt up to the third post hatched juvenile stage within a period of 90 days from the day of hatching as free swimming larval stage with 97% success. All the post hatched juveniles had similar morphological characteristics as that of the adults.  Over the past century, the dreadful conditions of habitat, especially the marine pollution, human exploitation for food and bio-medical production, loss of spawning and nursery grounds, has led to a decline in population of horseshoe crabs in many parts of the world and this species have been scheduled on the IUCN Red list and among them three ware categorized as data deficient .  The present work throws some light regarding the artificial rearing of trilobite larvae of T. gigas so as to successfully increase the population of such species in this part of globe. More works with large scale rearing strategy need to be done to achieve the targeted goal of sustainable maintenance of Indian horseshoe crabs. References

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